Resin reinforced zinc polycarboxylate temporary cement compositions and related kits and methods

ABSTRACT

Dental cement compositions (including two-part compositions), kits, and related methods are used for bonding a dental prosthetic appliance to a tooth. A first part includes an amine activator component and a zinc oxide reactive filler, while a second part includes a polymerization initiator (e.g., benzoyl peroxide) and a polymerizable component having a structure including at least one acrylate or methacrylate group at one end and a carboxylic acid group at another end. A temporary cement composition advantageously exhibits reduced compressive and/or bonding strength relative to permanent cement compositions, which provides sufficient strength to facilitate normal use of the teeth while the provisional appliance is in use, while also facilitating easy removal of the provisional appliance for replacement with a permanent appliance at a later time.

CROSS REFERENCE TO RELATED APPLICATION

This Application is a continuation of U.S. application Ser. No.11/680,284, filed Feb. 28, 2007, now issued U.S. Pat. No. 9,289,358, thedisclosure of which is incorporated herein in its entirety.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to dental restorations. More particularly,the invention relates to temporary cement compositions and related kitsand methods for temporarily bonding provisional dental restorativeappliances.

2. The Relevant Technology

When a dental practitioner performs a procedure requiring the removal ofa tooth or portion of a tooth, it is desirable to replace the tooth ortooth portion with a dental restorative appliance (e.g., a crown orbridge). Because permanent appliances typically take up to several weeksto prepare, the practitioner will sometimes fit a provisional applianceto replace the person's tooth until a permanent appliance is ready. Theprovisional appliance is intended to be a temporary prosthesis until apermanent appliance can be ordered and fabricated.

Because the provisional appliance is only intended for temporary use, itwould be an improvement in the art to provide a cement composition andrelated kits and methods that are specifically configured fortemporarily bonding a provisional appliance in place. Such a temporarycement would provide sufficient compressive strength and bondingstrength to allow the patient to engage in typical use of their teeth(e.g., biting, chewing, etc.) while also having sufficiently low bondingstrength characteristics so as to facilitate easily removal of theprovisional appliance by the practitioner when it is desired to replacethe provisional appliance with a permanent appliance.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to two-part resin-reinforced cementcompositions, kits, and related methods for bonding a dental prostheticappliance to a tooth. A first part includes an amine activator componentand a zinc oxide filler, while a second part includes a polymerizationinitiator (e.g., benzoyl peroxide) and a polymerizable component havinga structure including at least one acrylate or methacrylate group at oneend and a carboxylic acid group at another end. Such a molecule may havea linear structure so as to have just two ends, or it may be branched,so as to have more than just two ends. The two parts are initiallyseparate and then mixed together when it is desired to perform thetemporary bonding. Upon mixing the components together, the aminecomponent destabilizes the initiator, initiating curing of thepolymerizable component. The zinc oxide filler reacts with thecarboxylic acid group of the polymerizable component to further cure thepolycarboxylate temporary cement composition.

In one embodiment, the cement is a temporary cement composition used fortemporarily bonding a provisional dental prosthetic appliance to atooth. Such a temporary cement is advantageously relatively weak so asto allow easy removal of a provisional prosthetic and the composition.In one embodiment, the bonding strength and/or compressive strength isreduced to a desirable level by inclusion of a plasticizer and/or anun-reactive filler. In one example, a plasticizer is included so as tocomprise between about 15% and about 70% by weight of the composition,more preferably between about 25% and about 60% by weight of thecomposition, and most preferably between about 30% and about 40% byweight of the composition. In examples including an un-reactive filler,the un-reactive filler is preferably included so as to comprise betweenabout 3% and about 30% by weight of the composition, more preferablybetween about 5% and about 25% by weight of the composition, and mostpreferably between about 7% and about 20% by weight of the composition.In one currently preferred embodiment, both a plasticizer andun-reactive filler are included so as to collectively comprise at leastabout 35%, more preferably at least about 40% by weight of thecomposition, which the inventors have found advantageously decreasesbonding strength (and compressive strength if a plasticizer is included)of the composition as compared to a composition not including thesecomponents. For example, the plasticizer acts to reduce compressive andbonding strength as it weakens the cross-linked matrix structure of theresin reinforced zinc polycarboxylate cement, while the un-reactivefiller (e.g., a ceramic) serves to reduce cost and provide a desiredviscosity. The un-reactive filler may also act to increase compressivestrength and/or decrease bonding strength as compared to a compositionwhere all else is equal but without the un-reactive filler.

Contrasted with typical cement compositions, which have compressivestrengths of, for example, 100 MPa or more, the inventive temporarycement compositions have a compressive strength that is typically notgreater than about 70 MPa, more preferably not greater than 60 MPa, morepreferably not greater than about 30 MPa, and most preferably notgreater than about 20 MPa. The inventive compositions advantageouslyhave a relatively low bonding strength not greater than about 3 MPa,more preferably not greater than about 2.5 MPa, and most preferablybetween about 0.2 MPa and about 2 MPa, even more preferably betweenabout 0.2 MPa and about 1 MPa. Such reduced bonding strengthadvantageously allows the practitioner to easily remove the temporarycement and a provisional appliance restoration when needed (e.g., oncethe permanent appliance is ready for installation).

These and other advantages and features of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of the invention as set forthhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify the above and other advantages and features of thepresent invention, a more particular description of the invention willbe rendered by references to specific embodiments thereof, which areillustrated in the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope. The invention willbe described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIGS. 1A-1B illustrate exemplary systems including means for dispensingthe inventive two-part temporary cement composition;

FIG. 2A illustrates a plurality of teeth, one of which is in need ofrestoration;

FIG. 2B shows the broken tooth of FIG. 2A having been reduced and theresulting surface prepared in preparation for bonding a provisionaldental prosthetic appliance;

FIG. 2C illustrates an exemplary mixed temporary cement compositionbeing applied to the prepared tooth surface of FIG. 2B;

FIG. 2D illustrates a provisional dental prosthetic appliance beingpositioned for bonding;

FIG. 2E illustrates the provisional dental appliance bonded to thebroken tooth with the inventive temporary cement composition;

FIG. 3A illustrates the provisional dental appliance being removed fromthe broken tooth so as to allow placement and bonding of a permanentrestoration; and

FIG. 3B illustrates the permanent restoration bonded to the broken toothsubstrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS I. Introduction

The present invention is directed to a two-part resin-reinforced cementcomposition and related kits and methods for bonding a dental prostheticappliance to a tooth. The inventive composition is provided in twoparts. A first part includes an amine activator component and a zincoxide filler, while a second part includes a polymerization initiator(e.g., benzoyl peroxide) and a polymerizable component having astructure including at least one acrylate or methacrylate group at oneend and a carboxylic acid group at another end. Such a molecule may havea linear structure so as to have just two ends, or it may be branched,so as to have more than just two ends. The two parts are initiallyseparate, and are mixed together just prior to temporarily bonding theprovisional restoration. Upon mixing, the amine component destabilizesthe initiator, initiating curing of the polymerizable component. Thezinc oxide reacts with the carboxylic acid group to further cure thepolymerizable component.

II. An Exemplary Two-Part Temporary Cement Composition

The cement composition is provided in a chemical cure two part system. Achemical cure system is advantageous as it allows the cement compositionto cure even when not accessible to curing light wavelengths (i.e., itcan be quite difficult to effectively light cure through a temporarycrown or other provisional appliance). The first part advantageouslyincludes an amine activator component (e.g., a tertiary amine) and azinc oxide filler. Exemplary amine activator components include2,2-(p-Tolylimino)diethanol (P-TIDE), a tertiary amine available fromSigma Aldrich, located in St. Louis, Mo. Other exemplary tertiary aminesthat may be used include, but are not limited toN,N-Dimethyl-p-toluidine (DMPT) or Ethyl 4-(Dimethylamino)Benzoate(EDMAB).

The amine activator component is preferably included in an amountranging from about 0.01% to about 3% by weight of the composition, morepreferably between about 0.05% to about 2% by weight, and mostpreferably between about 0.1% and about 1% by weight of the composition.

The zinc oxide reactive filler is believed to react with the carboxylicacid group of the polymerizable component(s) within the composition soas to form a zinc polycarboxylate chelate structure. For this reason,the zinc oxide is initially separate from the polymerizable component(s)including an acrylate/methacrylate group at one end and a carboxylicacid group at another end. The total zinc oxide content (i.e., bothsides together) is preferably in an amount ranging from about 3% toabout 50% by weight, more preferably in an amount ranging from about 5%to about 30% by weight, and most preferably in an amount ranging fromabout 10% to about 20% by weight.

The second part of the two-part composition includes a polymerizationinitiator (e.g., a peroxide) and a polymerizable component having astructure including at least one acrylate and/or methacrylate group atone end (e.g., a HEMA group) and a carboxylic acid group at another end.The initiator (e.g., benzoyl peroxide, 2-butanone peroxide, lauroylperoxide, tert-butyl peroxide) is preferably included in an amountranging from about 0.01% to about 3% by weight of the composition, morepreferably between about 0.05% to about 2% by weight, and mostpreferably between about 0.1% and about 1% by weight of the composition.

Examples of such polymerizable components include, but are not limitedto mono-2-(methacryloyloxy)ethyl succinate (HEMA Succinate), availablefrom Sigma Aldrich, located in St. Louis, Mo.; and1,2-benzenedicarboxylic acidmono(2-((2-methyl-1-oxo-2-propenyl)oxy)ethyl)ester phthalic acid2-hydroxyethyl ester methacrylate (also known as2-hydroxyethylmethacrylate/phthalic anhydride, available from Esstech,located in Essington, Pa.

Mono-2-(methacryloyloxy)ethyl succinate has the structure shown below:

and 2-hydroxyethylmethacrylate/phthalic anhydride has the structureshown below:

The composition may advantageously include additional polymerizablecomponents, one or more of which may advantageously be capable ofcross-linking during polymerization. Examples of such polymerizablecomponents include various diacrylates and/or dimethacrylates, specificexamples of which include bisphenol-A glycidyl methacrylate (Bis-GMA),diurethane dimethacrylate (DUDMA), tri-ethylene glycol dimethacrylate(TEGDMA), hydroxyethyl methacrylate (HEMA) and/or glyceroldi-methacrylate (GDMA). Cross-linking during polymerization results inincreased overall bonding and compressive strength as compared toexamples including no cross-linking polymerizable components. Becausethese cross-linking polymerizable components tend to have relativelyhigh viscosities, it may be advantageous to also include one or morenon-cross-linking low viscosity polymerizable components (e.g.,hydroxypropylmethacrylate HPMA) that act as thinning agents so as toreduce the overall viscosity of the part in which it is included and/orthe overall composition. In addition, one or more of the polymerizablecomponents may be phosphated so as to increase adhesion of thecomposition to the tooth tissue.

The composition is advantageously characterized as having relatively lowbonding strength as compared to permanent bonding cements. In someembodiments, compressive strength may also be reduced as compared topermanent bonding cements. Advantageously, decreased strength(compressive and/or bonding) may be achieved through inclusion of asignificant fraction of un-reactive filler and/or plasticizer within thecomposition. Un-reactive ceramic filler may actually increasecompressive strength, while decreasing bonding strength. Plasticizers(e.g., a hydrocarbon such as polybutadiene or a polysorbate such asTWEEN-80) advantageously decrease both compressive and bonding strength.

Preferably, a temporary cement composition according to the inventionhas a compressive strength that is not greater than about 70 MPa, morepreferably not greater than about 60 MPa, more preferably not greaterthan about 30 MPa, and most preferably not greater than about 20 MPa.Compressive strengths within the range of about 15-30 MPa have beenfound to provide sufficient strength so as to withstand chewing, bitingand other forces typically encountered by a provisional dentalrestoration, while not being so strong as to present difficulties whenreplacing a provisional restoration with a permanent one.

Preferably, a temporary cement composition has a bonding strength thatis not greater than about 3 MPa, more preferably not greater than about2.5 MPa, and most preferably not greater than about 2 MPa. Bondingstrengths between about 0.2 MPa and about 2 MPa, even more preferablybetween about 0.2 MPa and about 1 MPa have been found to providesufficient strength so as to withstand chewing, biting and other forcestypically encountered by a provisional dental restoration, while notbeing so strong as to present difficulties when replacing a provisionalrestoration with a permanent one.

Permanent cement compositions characterized by higher compressive andbonding strengths are also within the scope of the invention. In such acomposition, the amount of plasticizer and/or un-reactive filler issignificantly reduced, particularly the amount of any includedplasticizer (which may be left out completely). Such permanent cementcompositions may include a compressive strength greater than about 70MPa, more preferably greater than about 85 MPa, and more preferablygreater than about 100 MPa, and bonding strengths preferably of at leastabout 3 MPa, more preferably at least about 3.5 MPa, and most preferablyat least about 4 MPa.

Exemplary plasticizers include, but are not limited to glycerin,HERCOLYN-D, a hydrogenated methyl ester of rosin marketed by HerculesChemical Company, aliphatic straight chain hydrocarbons such aspolybutadiene, cetyl alcohol, and/or TWEEN-80, a polysorbate. Because oftheir hydrophobic characteristics, an aliphatic hydrocarbon (e.g.,polybutadiene) is particularly preferred as it minimizes absorption ofsaliva and/or water from within the mouth. Preferably any plasticizer isincluded in an amount ranging from about 15% to about 70% by weight of atemporary cement composition, more preferably between about 25% to about60% by weight, and most preferably between about 30% and about 40% byweight of the temporary cement composition.

Exemplary un-reactive fillers include, but are not limited to ceramicfillers (e.g. any of various ceramic fillers sold under the trade nameZEODENT) available from J. M. Huber Corporation. Preferably anyun-reactive filler is included in an amount ranging from about 3% toabout 30% by weight of the composition, more preferably between about 5%to about 25% by weight, and most preferably between about 7% and about20% by weight of the composition. In one embodiment, the strengthreducing plasticizer and/or un-reactive filler collectively comprise atleast about 35% by weight of the composition, more preferably at leastabout 40% by weight of the composition.

The second part may further advantageously include water. Water isrequired by the zinc oxide chelating reaction in which the zinc becomesintegrated within the polycarboxylate matrix, and rather than relying onwater theoretically available from saliva within the patient's mouth,the water may be directly provided within the second part of thecomposition. This is further advantageous as the zinc oxide reaction isbelieved to occur mostly after the polymerization reaction has alreadybeen completed, requiring water from saliva to diffuse through thepolymerized material in order to participate in the zinc oxide reaction,which can weaken the strength of the polymerization bonds, and/or whichcan result in an insufficient quantity of water being made available forthe reaction. Including water within the composition avoids thesedisadvantages by shortening overall curing time and improving efficiencyand reliability of the cement composition. Water may be included withina range of about 0.05% to about 5% by weight of the composition, morepreferably about 0.1% to about 2% by weight, and most preferably about0.15% to about 0.5% by weight of the composition.

Additional components, for example, a rheology modifying component(e.g., fumed silica), colorants, flavorants, inhibitors (e.g., BHT), andother components may additionally be included. The inclusion of acolorant (e.g., a dye or pigment) within one or both parts (e.g., yellowwithin part 1 and blue within part 2) so as to give each part a colordifferent from the other part is advantageous as it provides a visualindicator that the two parts have been homogeneously mixed together.Examples of suitable pigments include Suncroma yellow iron oxide,available from Sun Chemical located in Parsippany, N.J.; V-9117 deeptan, V-9115 buff, and 41130A blue spersastain, available from FerroCorporation, located in Cleveland, Ohio. Additional colorants (e.g.,dyes and/or pigments) will be apparent to one skilled in the art.

III. Examples Example 1

An exemplary two-part temporary cement composition may be formed bymixing together equal weights of first and second parts as describedbelow:

Part A:

P-TIDE 0.5%  BisGMA 10% DUDMA  8% Zinc Oxide 25% Tween 80 55% Fumedsilica 1.5% Part B:

Benzoyl Peroxide 0.5%  HEMA Succinate 8% ZEODENT 113 45%  TEGDMA 8%Water 1.5%  Glycerin 30%  GDMA (phosphated) 7%

Example 2

An exemplary two-part temporary cement composition may be formed bymixing together equal weights of first and second parts as describedbelow:

Part A:

P-TIDE 0.5%  BisGMA 10% TEGDMA  8% Zinc Oxide 10% Tween 80 70% Fumedsilica 1.5% Part B:

Benzoyl Peroxide 0.5%  2-hydroxyethylmethacrylate/phthalic anhydride 10%ZEODENT 113 37% GDMA  8% HPMA 10% Water 4.5%  HERCOLYN-D 30%

Example 3

An exemplary two-part temporary cement composition was formed by mixingtogether equal weights of first and second parts as described below:

Part A:

P-TIDE 0.5%  BisGMA 34% TEGDMA 15% Zinc Oxide 29% ZEODENT 113 19%Suncroma yellow iron oxide pigment 0.075%   V-9117 deep tan pigment0.05  V-9115 buff pigment 0.0125 Fumed silica  2%Part B:

Benzoyl Peroxide 0.4% HEMA Succinate  12% GDMA (phosphated)  2% HPMA 10% Polybutadiene 66.57%  Water 0.5% Fumed Silica  7% 41130A bluespersastain pigment 0.035%  Almond oil flavorant 1.5%

The temporary cement composition was tested and found to have acompressive strength of about 17 MPa and a bonding strength of about 0.6MPa. Compressive strength was measured by placing the mixed two-partcomposition into a cylindrical mold and allowed to cure. After curing,the sample was removed from the mold and sanded with sand paper toreduce the cylinder to a cylinder having dimensions of 2.15 mm in heightand 2.35 mm in diameter. An INSTRON compressive strength measuringdevice was used to crush the sample so as to test compressive strength.Bonding strength was measured by performing a simulated “crown pull”test. The crown pull test was performed by shaping a human tooth into aconical shape. Using the cement composition to be tested, acorresponding metal simulated “crown” was cemented onto the tooth. TheINSTRON device was used to pull the crown off the tooth so as to testbonding strength. The fracturing occurred within the cement composition(i.e., not at the interface between the simulated metal “crown” and thecement. In measuring both compressive and bonding strength, each testwas performed multiple times and the results averaged. In addition, eachsample was soaked in water for 24 hours before being broken.

Example 4

An exemplary two-part temporary cement composition was formed by mixingtogether equal weights of first and second parts as described below:

Part A:

P-TIDE 0.5%  BisGMA 34% TEGDMA 15% Zinc Oxide 29% ZEODENT 113 19%Suncroma yellow iron oxide pigment 0.075%   V-9117 deep tan pigment0.05  V-9115 buff pigment 0.0125 Fumed silica  2%Part B:

Benzoyl Peroxide 0.4% HEMA Succinate  12% GDMA (phosphated)  2% HPMA 10% Polybutadiene 56.57%  Cetyl Alcohol  10% Water 0.5% Fumed Silica 7% 41130A blue spersastain pigment 0.035%  Almond oil flavorant 1.5%

The temporary cement composition was tested and found to have acompressive strength of about 29 MPa and a bonding strength of about 0.8MPa. In measuring compressive strength and bonding strength, the samemethology as described in conjunction with Example 3 was used.

IV. Exemplary Methods of Use

FIG. 1A illustrates an exemplary system 100 including a first syringe102 a and a second syringe 102 b in which the two-part composition iscontained. First syringe 102 a contains first part 104 a of thecomposition, while second syringe 102 b contains second part 104 b ofthe composition. As shown, quantities of each part may be dispensed andmixed on the surface of mixing pad 106 (e.g., with a mixing stick orother suitable tool).

FIG. 1B illustrates an alternative exemplary combination dispensing andmixing system 100′ including a first syringe barrel 102 a′ and a secondsyringe barrel 102 b′ which are integrally connected side by side. Suchan apparatus may be injection molded. First barrel 102 a′ contains firstpart 104 a of the composition, while second syringe 102 b′ containssecond part 104 b of the composition. As shown, quantities of each partmay be dispensed in an already mixed state as composition 104 frommixing and dispensing tip 105′ onto pad 106.

FIG. 2A is a perspective view of several of a person's teeth includingone broken tooth 220 in need of restoration. As shown in FIG. 2B, thebroken tooth 220 may be reduced and prepared as necessary (e.g.,insertion of a post and build up of core material around the post) andthe surface may be prepared (e.g., etched and primed) for bonding aprovisional dental appliance. As shown in FIGS. 2C-2D, mixed temporarycement composition 104 may be applied to the prepared tooth surface 222and/or the corresponding surface 224 of provisional appliance 250 a. Asshown in FIG. 2E, provisional appliance 250 a is bonded to toothsubstrate 220 with temporary cement 104.

Because of its relatively low bonding strength, temporary cement 104advantageously allows for easy removal of provisional appliance 250 aand replacement with a permanent appliance once the permanent appliancehas been prepared and is ready for installation. As shown in FIG. 3A,pliers or other means may be used to pull off provisional appliance 250a. Because of the relatively low bonding strength of temporary cementcomposition 104, separation easily and cleanly occurs at the bondinginterface 222. The permanent appliance 250 b may then be bonded using apermanent bonding cement (FIG. 3B).

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed is:
 1. An uncured dental cement composition, comprising:an amine activator component; zinc oxide; a polymerization initiatorcomprised of benzoyl peroxide; polybutadiene; and a polymerizablecomponent including an acrylate or methacrylate group and a carboxylicacid group.
 2. The uncured dental cement composition of claim 1, whereinthe uncured dental cement composition is a two-part compositioncomprising a first part initially separate from a second part, the firstpart comprising the amine activator component and the zinc oxide, andthe second part comprising the polymerization initiator and thepolymerizable component.
 3. The uncured dental cement composition ofclaim 1, wherein the benzoyl peroxide comprises between about 0.01percent and about 3 percent by weight of the cement composition.
 4. Theuncured dental cement composition of claim 1, wherein the zinc oxidecomprises between about 3 percent and about 50 percent by weight of thecement composition.
 5. The uncured dental cement composition of claim 1,the polymerizable component comprising the acrylate or methacrylategroup at one end and the carboxylic acid group at another end.
 6. Theuncured dental cement composition of claim 4, wherein the polymerizablecomponent comprises at least one of mono-2-(methacryloyloxy)ethylsuccinate or 2-hydroxyethylmethacrylate/phthalic anhydride.
 7. Theuncured dental cement composition of claim 1, further comprising across-linking polymerizable component.
 8. The uncured dental cementcomposition of claim 7, wherein the cross-linking polymerizablecomponent comprises at least one of bisphenol-A glycidyl methacrylate,diurethane dimethacrylate, tri-ethylene glycol dimethacrylate,hydroxyethyl methacrylate or glycerol dimethacrylate.
 9. The uncureddental cement composition of claim 7, wherein the cross-linkingpolymerizable component is phosphated.
 10. The uncured dental cementcomposition of claim 8, further comprising hydroxypropylmethacrylate.11. The uncured dental cement composition of claim 2, wherein at leastone of the first or second parts further comprises at least one of aplasticizer or an un-reactive filler in an amount so that the cementcomposition formed by mixing the first and second parts has a bondingstrength of less than 3 MPa when cured.
 12. An uncured dental cementcomposition, comprising: an amine activator component; zinc oxide; apolymerization initiator comprising benzoyl peroxide; a polymerizablecomponent having at least one acrylate or methacrylate group and also acarboxylic acid group; and a polybutadiene plasticizer.
 13. The uncureddental cement composition of claim 12, wherein the uncured dental cementcomposition is a two-part composition comprising a first part initiallyseparate from a second part, the first part comprising the amineactivator component and the zinc oxide, and the second part comprisingthe polymerization initiator and the polymerizable component, wherein atleast one of the first or second parts comprises the polybutadieneplasticizer.
 14. The uncured dental cement composition of claim 12,wherein the zinc oxide comprises between about 3 percent and about 50percent by weight of the cement composition.
 15. The uncured dentalcement composition of claim 12, wherein the polybutadiene plasticizer isincluded in an amount of from about 25% by weight to about 60% by weightof the cement composition.
 16. The uncured dental cement composition ofclaim 12, wherein the polybutadiene plasticizer is included in an amountof from about 30% by weight to about 40% by weight of the cementcomposition.
 17. The uncured dental cement composition of claim 12, thepolymerizable component comprising the acrylate or methacrylate group atone end and the carboxylic acid group at another end.
 18. The uncureddental cement composition of claim 17, wherein the polymerizablecomponent comprises mono-2-(methacryloyloxy)ethyl succinate and/or2-hydroxyethylmethacrylate/phthalic anhydride.
 19. The uncured dentalcement composition of claim 12, further comprising at least one ofbisphenol-A glycidyl methacrylate, diurethane dimethacrylate,tri-ethylene glycol dimethacrylate, hydroxyethyl methacrylate orglycerol dimethacrylate.
 20. The uncured dental cement composition ofclaim 13, wherein the cement composition formed by mixing the first andsecond parts has a bonding strength of less than 3 MPa when cured. 21.The uncured dental cement composition of claim 20, wherein the cementcomposition has a bonding strength of less than about 2.5 MPa whencured.
 22. An uncured dental cement composition comprising: an amineactivator component; zinc oxide; benzoyl peroxide; at least one ofmono-2-(methacryloyloxy)ethyl succinate or2-hydroxyethylmethacrylate/phthalic anhydride; and a polybutadieneplasticizer.
 23. The uncured dental cement composition of claim 22,wherein the uncured dental cement composition is a two-part compositioncomprising a first part initially separate from a second part, the firstpart comprising the amine activator component and the zinc oxide, andthe second part comprising the benzoyl peroxide and the at least one ofmono-2-(methacryloyloxy)ethyl succinate or2-hydroxyethylmethacrylate/phthalic anhydride, wherein at least one ofthe first or second parts comprises the polybutadiene plasticizer. 24.An uncured dental cement composition, comprising: an amine activatorcomponent; zinc oxide; a polymerization initiator comprised of benzoylperoxide; and a polymerizable component including an acrylate ormethacrylate group and a carboxylic acid group, wherein the cementcomposition, when applied to a tooth and cured, has a bond strength thatis not more than about 2.5 MPa.